Abstract
Nanowire field emitters have great potential for use as large-area gated field emitter arrays (FEAs). However, the micrometer-scale cathode patterns in gated FEA devices will reduce regulation of the gate voltage and limit the field emission currents of these devices as a result of field-screening effect among the neighboring nanowires. In this article, a ring-shaped ZnO nanowire pad is proposed to overcome this problem. Diode measurements show that the prepared ring-shaped ZnO nanowire pad arrays shows uniform emission with a turn-on field of 5.9 V/µm and a field emission current density of 4.6 mA/cm2 under an applied field of 9 V/µm. The ZnO nanowire pad arrays were integrated into coplanar-gate FEAs and enhanced gate-controlled device characteristics were obtained. The gate-controlled capability was studied via microscopic in-situ measurements of the field emission from the ZnO nanowires in the coplanar-gate FEAs. Based on the results of both simulations and experiments, we attributed the enhanced gate-controlled device capabilities to more efficient emission of electrons from the ZnO nanowires as a result of the increase edge area by designing ring-shaped ZnO nanowire pad. The results are important to the realization of large-area gate-controlled FEAs based on nanowire emitters for use in vacuum electronic devices.
Highlights
Large-area gated field emitter arrays (FEAs) are important for applications in vacuum electronic devices such as flat panel X-ray sources, imaging detectors, field emission displays (FEDs) and light sources[1,2,3,4,5,6]
ZnO nanowires can be synthesized by various methods, including thermal evaporation/condensation[12], chemical vapor deposition[13], hydrothermal solution[14], and thermal oxidation[15], which indicate the feasibility of integration of these nanowires in device structures[16,17]
The results show that the field emission currents of these four regions increase with increasing gate voltage, and when the gate voltage increases to 80 V, the currents of regions A, B, C and D are 77, 80, 85 and 190 pA, respectively
Summary
Large-area gated field emitter arrays (FEAs) are important for applications in vacuum electronic devices such as flat panel X-ray sources, imaging detectors, field emission displays (FEDs) and light sources[1,2,3,4,5,6]. Enhancement of the regulation of the gate voltage to improve the field emission current would be one way to improve the performance of the resulting gated nanowire FEAs. In this work, a ring-shaped ZnO nanowire pad structure is proposed with the intention of providing enhanced gate voltage regulation. Microscopic in-situ field emission measurements of the ZnO nanowires in various regions of the ring-shaped ZnO pad in the coplanar-gate FEA under various gate voltages were conducted in an ultrahigh vacuum system and the results verified our proposed structure
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